[Resource Topic] 2021/1565: Practical, Round-Optimal Lattice-Based Blind Signatures

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Practical, Round-Optimal Lattice-Based Blind Signatures

Authors: Shweta Agrawal, Elena Kirshanova, Damien Stehle, Anshu Yadav


Blind signatures are a fundamental cryptographic primitive with numerous practical applications. While there exist many practical blind signatures from number-theoretic assumptions, the situation is far less satisfactory from post-quantum assumptions. In this work, we provide the first overall practical, lattice-based blind signature, supporting an unbounded number of signature queries and additionally enjoying optimal round complexity. We provide a detailed estimate of parameters achieved – we obtain a signature of size less than 44KB, for a core-SVP hardness of 109 bits. The run-times of the signer, user and verifier are also very small. Our scheme relies on the Gentry, Peikert and Vaikuntanathan signature [STOC’08] and non-interactive zero-knowledge proofs for linear relations with small unknowns, which are significantly more efficient than their general purpose counterparts. Its security stems from a new and arguably natural assumption which we introduce, called the one-more-ISIS assumption. This assumption can be seen as a lattice analogue of the one-more-RSA assumption by Bellare et al [JoC’03]. To gain confidence in our assumption, we provide a detailed analysis of diverse attack strategies.

ePrint: https://eprint.iacr.org/2021/1565

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